The subject invention pertains to spunbond polyester mats with an improved binding composition. More specifically, the invention pertains to spunbond polyester mats using an improved curable composition comprising an amine salt of an inorganic acid. An aldehyde or ketone is added to the salt to form a composition which upon curing is capable of forming a water-insoluble polymer. Once applied to the polymer fibers, the binding composition is cured.
Spunbond polyester nonwovens are known and commercially available. The unique technology process creates products with the excellent properties of a uniform surface, tear strength and high porosity. Polyester spunbond is a manufactured sheet of randomly oriented polyester filaments bonded by calendaring, needling, chemically with a binder, or a combination of these methods. In general, small diameter filaments are formed by extruding one or more molten polyester fibers from a spinneret. The extruded fibers are cooled while being drawn to form spunbond fibers or continuous filaments, which are deposited or laid onto a forming surface in a random manner to form a loosely entangled web. This web is then subjected to a bonding process.
When a binder is used thermosetting binders are employed as bonding agents in curable polyester spunbond mats for reinforcement applications. Generally, latex binders have been employed to bind polyester fibers. These latex binders are crosslinked via several mechanisms including formation of ester, ether, alkyl, epoxy and urethane linkages. Most latex binders are crosslinked via addition of a formaldehyde based crosslinker. Since formaldehyde is a known respiratory and skin irritant as well as a suspected carcinogen, it is desirable to eliminate formaldehyde based binders from the manufacturing process for these products. While other formaldehyde free binders are available to produce spunbond products, these binders typically result in reduced physical performance or greater difficulty in processing the mat. Thus, it is highly desirable to have a mat binder that does not contain formaldehyde in its formulation or a binder that produces or generates formaldehyde in the curing or crosslinking step. Such a binder should process easily and demonstrate equivalent performance to formaldehyde-based binders. Although existing binders provide adequate tensile and tear strength to the spunbond mat, thermal dimensional stability (TDS) requirements at temperatures above 180° C. can not be met and as a result, fiberglass scrim reinforcement is often required.
Accordingly, in one aspect the present invention provides a spunbond polyester mat comprised of a binder which is free of formaldehyde.
Another aspect of the invention provides a novel spunbond polyester mat with a formaldehyde free binder that processes easily and provides at least comparable tensile and tear strength to the mat.
Still another aspect of the present invention is to provide a spunbond polyester mat which uses a suitable binder having improved economics, while also enjoying improved thermal dimensional stability.
These and other aspects of the present invention will become apparent to the skilled artisan upon a review of the following description and the claims appended hereto.